Crankshaft won’t turn over freely by hand during timing belt replacement

[rustybolts924s]

I am attempting to replace the timing belt on my 1987 924s for the first time. So far I have removed all the components from the front of the engine and removed the starter. I began the procedure to set the engine to Top Dead Center. As I rotated the engine CW it started smoothly and then gained a large resistance about 1/5 of a turn in. Do large that I was unable to rotate the engine any further. I then rotated it back CCW and when I hit 1/5 turn back the same thing happened. It feels like there is a spring at each side of the rotation keeping me from going any further. I did not put too much pressure at the “springy” point as I am afraid the positions and the valves are hitting. I am confused about why this is happening, I am all ears to any ideas of why this may be happening. Thank you in advance for all the help!

Some background, the car was running and driving before I began the procedure. I did remove the spark plugs before spinning the engine by hand. This is also the first time I have ever attempted to change a timing belt for any vehicle.

[P_Coastal]

I am sure one of our experts will be along soon.
In the meantime, welcome to Carpokes

[Tom]

My strong suspicion is that you are just feeling the engine compression that peaks every 180 degrees. Sounds like you have a healthy engine. If you want to confirm, just remove the spark plugs and my guess is that springy feeling will completely disappear. Just be sure to put the plugs back in before replacing the timing belt, as the factory tensioning system assumes that level of 'pull' on the belts.

[rustybolts924s]

Thank you for the quick reply! It seems to still have the springy feeling even though I removed the spark plugs. It seems my engine health is so good it has compression without spark plugs .

[Tom]

Ok, um.... is it in gear?

[dr bob]

First, Welcome to Carpokes!

I had to reread your description a couple times to make sure I didn't miss anything. Still a question -- Did you remove the timing belt before attempting to rotate the engine to TDC? My memory of the 924 is that it's not normally an interference engine, but I also can't remember the last time my memory was good. Regardless, we try to get the crankshaft and cam to TDC on #1 cylinder before we remove the belt and the other moving components from the front of the engine. Non-interference engines are less critical, but it still makes the job a whole lot easier if you don't have so much fight against valve spring pressure getting things to line up correctly again.

More, and under the list of stupid stuff I've done but don't regularly admit to --

-- Is the transmission in gear?

-- I take spark plugs out so I have less 'work' to do rotating the crankshaft for both initial indexing and final spinning for confirmation with the new belt in place.

-- Even with plugs out, the friction of pistons moving in the bores is hardly linear. I still expect the torque necessary to move the crank to vary as I rotate it.


My first timing belt project on the V8 in my 928 was a bit of a nail-biter, even with the Workshop Manual and several very detailed user procedures. I read through each of those several times to make sure I had the best possible understanding of all the steps. Plus I ran three video cameras with extra lighting and a headset microphone, so I could document the process for myself and possibly for others. I used the video several times for some clues on how specific pieces needed to go back together, very handy.

For your car, the engine stuff is common with the engine family, so there are many procedure resources available online. Most Important will be the best workshop manual, and one or two user procedures that might offer a more nuanced detail or two.

What to do now --

-- Make darn sure that nothing has fallen into a spark plug hole to a cylinder. I use a cheapie inspection camera for this, through the plug hole. My camera has a small 45º mirror attachment that lets me see across the top of the piston to look for debris. Easiest with the piston somewhere close to top of stroke.

-- The four-cylinder engine has two pistons indexed in one plane, and the other two 180º away. Piston friction is lowest near end of stroke, highest mid-stroke when all of them are trying to move at the end of the horizontal (in the block) crankshaft throws. Easiest with the mark on the balancer at TDC or 180º from TDC, hardest with the mark at 90º either side of the TDC mark.

-- If you truly are feeling a solid hard point in the rotation, it's a mechanical not a friction issue. It's been forever since I worked on an inline 4, so I don't remember the options for valve-to-piston interference.

-- For interference engines. if you removed the belt at some random not-at-TDC #1 point, you can rotate the crankshaft gently to the closest (to where it is now) point 90º before or after the TDC mark, then safely spin the cam to its correct indexed TDC #1 position. Then bring the crankshaft to TDC#1 mark and install the belt normally. With the crank 90º off TDC either way, all the pistons will be down in the bores with no worries about bending valves while you move the cam.


TL;DR, may be traumatic to small children and sensitive adults --

I had a longtime Lotus habit that I fed way too much. The first one 'landed' on me almost by accident, when a person I'd met needed to sell his car in a hurry. Going through the easy stuff on the engine, like verifying float and needle-and-seat in a carburetor still on the engine, I apparently dropped a small accelerator-pump check ball down the intake, where it passed the throttle plate, a valve, and ended up in a cylinder. Then same symptom you describe, where there's a 'hard point' in the crank rotation. I decided to just muscle it past that, inadvertently damaging both the head and the piston in the process, plus cracking the drop-in liner. Telltale then was a cylinder full of coolant and a mini flood from the exhaust. It was a pretty expensive day, not at all what a finances-limited student needed at that particular time. The lesson was learned though, about making sure things spin correctly by hand at every possible opportunity during assembly. And making sure I find any possible causes before proceeding.


Do keep the thread updated with what you find, and the progress you are making. The Carpokes community is here because of a shared love of the cars and compassion for owners. fire a flare here if you get stonewalled, and maybe get an extra set of eyes and hands to help you figure it out in vitro.

-- I see that others have shared clues while I was typing...

[rustybolts924s]

It was in gear! Once I took it out the engine spun freely. Oh what a rookie mistake. Thank you @Tom and @dr bob!

[Tom]

Great. Your clutch passed its first test.

And just for prosperity, the '87 924S is essentially a 944 without fender flares, complete with a full-fledged 944 interference engine... Porsche said they needed an entry level car. I think they were using up pre-85 interior parts and 924 fenders.

[ROB III]

@rustybolts924s
Look at it this way, we have all made rookie mistakes (I do frequently) on the way to becoming better mechanics, proficient in diagnostic skills, and a shepherd of skill and knowledge in our quest to become an expert.
Now that your specific issue has been shared, diagnosed, and learned, you are one step closer to being an expert!
One of the great aspects of the CARPOKES universe is the members understanding of not knowing and where to turn for help and advice with no backlash.
Thank you for joining and sharing!

[Tom]

@rustybolts924s
Look at it this way, we have all made rookie mistakes (I do frequently) on the way to becoming better mechanics, proficient in diagnostic skills, and a shepherd of skill and knowledge in our quest to become an expert.
Now that your specific issue has been shared, diagnosed, and learned, you are one step closer to being an expert!
One of the great aspects of the CARPOKES universe is the members understanding of not knowing and where to turn for help and advice with no backlash.
Thank you for joining and sharing!

Well said Rob. People look the smallest when trying to belittle others.